[ALSA] snd_hda_intel: fix for intel imac

Add handling of Intel-iMac-specific pinconfig of the sound card.
Intel-iMac now handled as a separated subsystem.

Signed-off-by: Sylvain FORET <sylvain.foret@anu.edu.au>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>